Prestressing reinforcing device for concrete



H. SCHORER Aug. 31, 1943.

Original Filed Aug. 14. 1941 m m m w m NH T. & N Al W m I H WWWWW M W -gw Iii ..,1 2 509 4 Q Q Q Q. wwwmx mwfi N? & w 1% Q Q Patented Aug. 31, 1943 UNITED STATES PATENT OFFICE PRESTRESSING BEINFORCING DEVICE FOR CONCRETE Herman Schorer, Valhalla, N. Y. Application August 14, 1941, Serial No. 406,806

13 Claims.

The present invention relates to improvements in a prestressing reinforcing device for concrete. The present application is a continuation in part of my copending application Ser. No. 320,028, filed February 21, 1940.

An object of the invention is the provision of a prestressing mechanism comprising a central compression member, a plurality of tension members disposed therearound and spaced therefrom by means of a plurality of spacer members, and a device for holding one end of said tension members, for stretching said tension members, and for transmitting the tension force reaction to said compression member whereby all tension members are stressed uniformly and simultaneously and stability of the compression member is assured. To achieve this, the device according to the invention simultaneously grips with equal force and firmly holds the ends of all tension members which members preferably consist of high strength steel wire, such as spring wire, music wire, etc., or braided and rope-like combinations thereof. With the device according to the invention, no relative slipping of the individual tension members can take place under any stress conditions. The entire stretching mechanism according to the invention is confined within a comparatively small space in order to permit close placing of a plurality of precompressing mechanisms in a mass of concrete. The device according to the present invention is also adapted to accurately control and measure the applied stretching force and to provide simple means for its release after the concrete has reached the desired compressive strength. Instead of steel, the tension members may be made of other materials of high tensile strength and qualified to bind with concrete, such as glass, fibre-glass, and the like.

The improved prestressing mechanism according to the invention consists essentially of a ring wedge device which firmly holds and simultaneously grips the ends of the tension members, of means for the application and release of the gripping force, and of means for the application and release of the stretching force in the tension members.

A further object of the present invention is the provision of an improved anchorage device for holding the other ends of the tension members which are not engaged by the aforesaid stretching and tension reaction transmission device. This device also makes use of a ring wedge construction which simultaneously grips with equal force and holds the far ends of all tension members and also holds the far end of the compressloii mem- -ber in definite central position with respect to the tension members.

Another object of the present invention is the provision of an improved compression member arrangement which permits drawing oil of excess water and air from the plastic concrete mass which surrounds the compression member.

An object of the present invention resides in the provision of simplified spacer members for holding the tension members in desired position relatively to the compression member.

Further and other objects of the present invention will be hereinafter set forth in the accompanying specification and claims and shown in the drawing which, by way of illustration, shows what I now consider to be a preferred embodiment' of my invention. a

In the drawing:

Fig. 1 is a longitudinal part sectional view of a prestressing unit according to the invention.

Fig. 2 shows a spacer member according to the invention in large scale.

Fig. 3 is a large scale part sectional view of a ring wedge device according to the invention.

Fig. 4 is a longitudinal sectional view of the device shown in Fig. 3.

Fig. 5 is a diagrammatic showing'of a hydraulic I mechanism for operating the tensioning and tensioning reaction in Fig. 1. Like parts are designated by like numerals in all figures of the drawing.

Referring particularly to the drawing, the stressing and tension force transmitting device shown on the right side of Fig. 1 comprises a ring wedge device for simultaneously gripping and holding one end 01 all tension members l3 and i3. This device is also separately shown in Figures 3 and 4. It consists of a plurality of conical wedge members I having annulus-sectorlike cross sectional configuration and being disposed symmetrically about the center line of the compression or stay member Id. The outside wedge surfaces l' and I" are parts of a double cone and the inside surfaces form a cylindrical cavity. The radial faces of members I are provided with longitudinal, groove-like depressions 2, the groove surfaces being made rough, for instance by means of knurling or threading. The groove surfaces are of sufiicient hardness to "bite into the tension members [3 upon application of the gripping force.

The radial faces of members I are further provided with pockets 3, which receive compression force transmitting device shown springs 4 and internal spring guides 5. A circumferential groove 6 permits assembly of the wedges inside the holding ring 1 whereby relative movement of the individual wedges in a longitudinal direction is prevented. The compression springs 4 have the tendency to widen the space between adjacent wedges. The resulting radial, outward movement of the wedges is limited by the holding ring I. In this position the tension wires l3 and I3 can then be conveniently inserted in the space formed by opposite grooves 2.

The wedge assembly is located between two rings or counter members 8 and 9, which have conical inside surfaces corresponding to the outside wedge surfaces. The outside surfaces of rings 8 and 9 are cylindrical. Ring 8 is fixed in a sleeve II), for instance by means of a press fit, and abuts shoulder I9 provided on said sleeve. Ring 9 is movable in a longitudinal direction, such movement being limited by a washer I l disposed between ring 9 and a cylindrical and threaded member l2 screwed in member Ill.

After insertion of the tension members l3 and I3 in the groove spaces 2, the threaded member I2 is turned so as to force ring 9 toward ring 8.

Due to the conical contact surfaces a radial force component is exerted on wedge members I which force counteracts the spreading force of springs 4 thereby reducing the radial space between the wedges and exerting a gripping force on the tension member l3 and I3 disposed in grooves 2.

The magnitude of the gripping force is mainly determined by the cone angles of the rings 8 and 9, the frictional .resistance on the conical contact surfaces, and by the angle formed by the radial faces of the wedge members. The result is a powerful double wedge action which permits the simultaneous and uniform gripping of all tension members within a very confined space.

A hollow ram member I5 is screwed into the threaded member l2, thereby forcing a cap [6 toward the compression or stay member, M. The reaction of this compression force is transmitted through the sleeve Ill, ring 8 and wedges l to the ends of the tension members I3 which are subjected to the desired tensile stress. As may be readily seen, tensioning of members i3 has the tendency to increase the gripping effect of wedges I. The stretching operation is facilitated by the application of a hydraulic ram,

which also permits accurate control of the stretching, force by simply reading a pressure gauge 35 which may be connected to the actuating fluid space. For this purpose a yoke I1 is attached to member l2 by means of threads H. A pusher pin l8 extending from the ram plunger 36 is inserted into the hollow bolt member I5. left as seen in Fig. 5 the pusher pin l8 presses against cap l6 and the reaction is transmitted through the yoke to member l2 and to the ends of the tension members as described above. The bolt member l5 can then-be turned freely to follow the movement of cap l6, holding said cap in position when the hydraulic ram is re- When the ram plunger moves to the moved. The hydraulic mechanism is shown in Fig. 5.

The release of the stretching force and the release of the gripping force on the tension members are carried out in reverse order.

In the proposed prestressing mechanism the stay or compression member consists of a tube M on which are disposed spacers 20 at suitable intervals. Between the spacers the tube is surrounded by a sheathlike member 2| made of filter fabric and separated from the tube i4 and supported by a helically wound wire 22 which has the shape of a compression spring. The ends of the filter 2| are extended and fastened over the projections 20' of adjacent spacers so as to prevent cement mortar from entering the inside space of the filter fabric. The wall of the compression member 14 is provided with small perforations 23 at suitable intervals. The end caps 16 are provided with a suction hose connection.

The compression member I4 is adapted to fulfill its primary function as an efficient column, and, in addition, can also be utilized as a conduit for drawing ofi? excess water and air from the surrounding plastic concrete mass.

After the prestressing mechanism has been embedded in fresh concrete and before the latter has set, a suction hose is attached to cap l6,

-' whereby the air inside the tubular member it and filter tube 2| is exhausted. The resulting pressure difference between the outside and inside of the filter fabric forces excess water and embedded air from the surrounding plastic concrete through the filter fabric, whereupon it flows along the helical space and through'the perforations 23 into the tubular conduit and suction hose.

Due to the outside atmospheric pressure the space around the compression member I 4 and the tension members [3 and I3, is thoroughly filled with a very compact concrete mixture, completely embedding the tension members over their entire length. The removal of excess water and air thus improves the compressive strength and textture of the concrete at themost desirable location, namely along the zones of maximum stress upon release of the stretching force. At the same time it is assured, as experience has shown, that the compression member M can be removed without difiiculty. If desired the resulting cavity may then be filled with cement grout under pressure.

The spacer members 20 shown separately in Fig. 2 are of star-like configuration having prongs 30 provided with recesses 31 over which one set of tension wires, namely wires iii are laid. In the recesses 32 between the prongs rests the other set of the tension wires which are designated by numeral l3.

At the far end of th device, on the left side of Fig. 1, an end anchorage mechanism is provided comprising a ring-wedge device which is alike the one used at the right side. and simultaneously grips the far end of the tension members l3'and l3. It is placed within a sleeve member 33 having a shoulder 34 which the cone ring member 8 abuts in the same way as member 8 abuts shoulder i9. Member 33 has a nutlike portion 24 into which a bolt member 25 is screwed which has a recessed portion 2'! for abutting and holding compression member I4 in place. Between bolt member 25 and cone ring member 9' a washer 28 is inserted which corresponds to the annular member ll of the stretching mechanism. Members 1' and 1' correspond to mem- This device uniformly asaaoss berslandl stretching mechanism on the right sideof Fig. 1. The stretching mechanism shown on the right side as well as the anchorage mechanism shown on the left side of Fig. 1 is disposed outside of boards 28 and 29 respectively which form the concrete mould. Both mechanisms can be removed after they have fulfilled their duty and reused.

While I believe the above described embodiment of my invention to be a preferred embodiment, I wish it to be understood that I do not desirgrto be limited to the exact details of design an construction shown and described, for obvious modifications will occur to a person skilled in the m I claim: a

1. A prestressing and reinforcing device for concrete comprising a compression member, a plurality of tension members spaced from and disposed around said compression member, a tensioning andtensioning force transmitting mechanism disposed at one end of said device and interconnecting one end of said tension members and one end of said compression member and tensioning said tension members and transmitting th tension reaction force to said compression member, and an anchorage mechanism disposed at the other end of said device and interconnecting the other end of said tension members and of said compression member, each of said mechanisms comprising a ring wedge device simultaneously gripping with equal force and firmly holding the ends of all of said tension members, said ring wedge device including a, plurality of wedge members disposed between and clampingly engaging the ends of said reinforcing members and having an annulus-sector like cross section and forming together a substantially cone shaped outer surface disposed coaxially with said device, a counter member having a substantially cone shaped inner surface disposed coaxially with and engaging said outer surafce, and tightening means engaging said wedge members and said counter member and forcing them in axial direction toward one another whereby said wedge members are moved radially and toward one another and toward said tension members.

2. In a prestressing and reinforcing device for concrete comprising a compression member and a plurality of tension members spaced from and disposed around said compression member, a ring wedge device comprising a plurality of individual wedge members having an annulus-sector-like cross sectional configuration and being disposed around said compression member and between said tension members and having an outer surface inclined to the longitudinal axis of said wedge device, said inclined surfaces forming together a cone surface, and an annular member having a cone shaped interior surface corresponding to and slidingly engaging said outer surfaces of said wedge members and forcing said wedge members together and toward said tension members upon relative axial movement of said ring member and said wedge members.

3. In a prestressing and reinforcing device for concrete comprising a compression member and a plurality of tension members spaced from and disposed around said compression member, a ring wedge device comprising a plurality of individual wedge members having an annulus-sector-like cross sectional configuration and being disposed around said compression member and between said tension members and having outer surfaces inclined to the longitudinal axis of said wedge device and forming together a double cone surface, and two annular members each having a cone shaped interior surface corresponding to and slidingly engaging one of the said outer surfaces of said wedge members and forcing s aid wedge members together and toward said tension members upon relative axial movement of said ring members and-said wed e members.

4. In a prestressing and reinforcing device for concrete comprising a compression member and a plurality of tension members spaced from and disposed around said compression member, a ring wedge device comprising a plurality of individual wedge members having an annulus-sectorlike cross sectional configuration and being disposed around said compression member and between said tension members and having an outer surface inclined to the longitudinal axis of said wedge device, said surfaces forming together a cone surface, an annular member having a cone shaped interior surface corresponding to and slidingly engaging said outer surfaces of said wedge member and forcing said wedge members together and toward said tension members upon relative axial movementof said ring member and said Wedge members, a ring member holding said wedge members together, and resilient members disposed between said wedge members and forcing said members apart and toward said ring member.

5. In a prestressing and reinforcing device for concrete comprising a compression member and a. plurality of tension members spaced from and disposed around said compression member, a ring wedge device comprising a plurality of individual wedge members having an annulus-sector-like cross sectional configuration and being disposed around said compression member and between said tension members and having an outer surface inclined to the longitudinal axis of said wedge device, said outer surfaces forming together a cone surface, and an annular memberhaving a cone shaped interior surface corresponding to and slidingly engaging said outer surfaces of said wedge members and forcing said wedge members together and toward said tension members upon relative axial movement of said ring member and said wedg members, said wedge members having rough surfaced longitudinal recesses on their radial surfaces receiving and firmly engaging said tension members.

6. In a prestressing and reinforcing device for concrete comprising a compression member and a plurality of tension members spaced from and disposed aroundsaid compression member, a tensioning and tensioning force transmitting mechouter surfaces of said wedge members, a cylindrical member disposed around said wedge device and of said annular members, substantially cylindrical means longitudinally movably inserted in said cylindrical member and abutting the other of said annular members, said cylindrical member having an interior shoulder abutting one toward one mother, forcing said annular mem-- bers together and said wedge members simultaneously toward saidtension member for firmly gripping the latter, a ram means in said cylindrical means abutting one end of said compression member, and a holding member holding said ram means in desired position relatively to said cylindrical means.

7. In a presetressing and reinforcing device for concrete comprising a compression member and a plurality of tension members spaced from and disposed around said compression member, a tensioning and tensioning force transmitting mechanism comprising a ring wedge device including a plurality of individual wedge members having an annulus-sector-like cross sectional configuration and being disposed around said compression member and between said tension members and having outer surfaces inclined 'to the longitudinal axis of said wedge device and forming together a double cone surface, and two annular members each having a cone shaped interior surface corresponding to and slidingly engaging one of the said Outer surfaces of said wedge members, a nut member disposed around said wedge device and having an interior shoulder abutting one of said annular members and having an internal thread, and nut means having an external thread engaging the thread of said nut member and abutting the other of said annular members and having, an internal thread, said nut member and said not means, upon axial movement toward one another, forcing said annular members together and said wedge members simultaneously toward said tension members. for firmly gripping the latter, ram means in said nut means abutting one end of said compression member and comprising externally threaded means screwed into the internal thread .of said nut means, said ram means upon longitudinal relative movement with respect to said nut means pulling and tensioning said tension members and transmitting the tension reaction force to said compression members.

8. A prestressing and reinforcing device for concrete comprising a tubular compression member having lateral perforations, a plurality of ten sion members disposed around said compression member, spacer members disposed on said compression member and spaced from one another and spacing said tension members from said compression member, a tensioning and tensioning force transmitting mechanism disposed at one ,end of said device and interconnecting one end of said tension members and one end of said compression member and tensioning said tension members and transmitting the tension reaction force to said compression member, an anchorage mechanism disposed at the other end of said device and interconnecting the other end of said tension members and the other end of said compression member, and tubular members permeable to water and air disposed around said comression member and between said spacer members.

9. A prestressing and reinforcing device for concrete comprising a tubular compression member having lateral perforations, a plurality of tension members disposed around said compression member, spacer members disposed on said compression member and spaced from one another and spacing said tension members from said compression member, said tubular members, and a tensioning and tensioning force transmitting mechanism disposed at one end of said device and interconnecting one end of said tension members and one end of said compression member and tensioning said tension members and transmitting thetension. reaction force tosaid compres- .sion member, an anchorage mechanism disposed at the other end of said device and interconnecting the other end of said tension members and the other end of said compression member, tubu-' lar members permeable to water and air disposed around said compression member and between said spacer members, and helical spacing means disposed between'said compression member and said tubular members.

10. A prestressing and reinforcing device for concrete comprising a tubular compression member having lateral perforations, a plurality of tension members disposed around said compression member, spacer members disposed on said compression member and spaced from one another and spacing said tension members from said compression member, a tensioning and tensioning force transmitting mechanism disposed at one end of said device and interconnecting one end of said tension members and one end of said compression member and tensioning said tension members and transmitting the tension reaction force to said compression member, an anchorage mechanism disposed at the other end of said device and interconnecting the other end of said tension members and the other end of saidcompression member, and tubular members permeable to water and air disposed around said compression member and between said spacer members, said spacer members having tubular projections disposed around said compression member and extending into said tubular members.

11. A prestressing and reinforcing device for concrete comprising a longitudinal compression.

member, two sets of tension member disposed around said compression member, spacer members disposed on said compression member and spaced from one another, a tensioning and tensioning force transmitting mechanism disposed at one end of said device and interconnecting one end of said tension members and one end of said compression member and tensioning said tension members and transmitting the tension reaction force to said compression member, and an anchorage mechanism disposed at the other end of said device and interconnecting the other ends.

of said tension members and the other end of said compression member, said spacer members having prong portions engaging one set of said tension members and recesses between said prong portions accommodating the other set of said tension members.

12. A prestressing and reinforcing device for concrete comprising a compression member, a plurality of tension members spaced from and disposed around said compression member, a tensioning and tensioning force transmitting mech anism disposed at one end of said device and 'interconnecting one end of said tension members and 'one end of said compression member and tensioning said tension members and transmitting the tension reaction force to said compression member, and an end mechanism disposed at the other end of said device and interconnecting the other end of said tension members and the other end of said compression member, said end mechanism comprising a ringwedge device including a plurality of wedge members disposed around said compression member and between said tension members and having annulus-sectorlike cross sectional configuration and two outer surfaces inclined in opposite direction with'respect to the longitudinal axis or said device and forming together a double cone outer surface, two annular members having internal conical surfaces corresponding to and individually slidingly engaging the outer surfaces of said double cone, a nut member disposed around said wedge device and having an internally projecting shoulder abutting one of said annular members, and bolt means screwed into said nut member and abutting the other oi said annular members and said other end oi said compression member.

13. A prestressing and reinforcing device for concrete comprising a compression member, a plurality oi tension members spaced from and disposed around said compression member, a tensioning and tensioning force transmitting mechanism disposed at one end of said device and interconnecting one end of said tension members and one end of said compression member and tensioning said tension members and transmitting the tension reaction force to said compression member, and an end mechanism disposed device and interconnecting the other end of said tension members and the other end of said compression member, said end mechanism comprising a ring wedge device including a plurality of wedge members disposed around said compression member and between said tension members and having annulus-sector-like cross sectional configuration and two outer surfaces inclined in opposite direction with respect to the longitudinal axis of said device and at the other end of said forming together a double cone outer surface, two 

